1. Technical Field
The disclosure and claims generally relate to construction materials and techniques, and more specifically relate to a method for making a concrete block.
2. Background Art
Building blocks have been used for centuries to construct homes, office buildings, churches, and many other structures. Early building blocks were hewn from stone into appropriate shapes that were assembled together, typically using mortar, to form a wall. In modern times, various types of concrete blocks were developed, which are typically formed by pouring a cement mixture into a mold and allowing the cement to harden. This type of cement block is strong and makes for a sturdy wall, but installing a traditional concrete block requires a skilled mason that places mortar in all joints between blocks to secure the blocks in place.
Various different block configurations have been developed that allow mortar to be poured into inner passageways of the blocks once the blocks have been constructed into a wall. Some of these eliminate the need for a mason to apply mortar between the blocks as the blocks are laid because the blocks are interlocked using mortar poured into interior passages. Examples of blocks with inner passages are found in U.S. Pat. No. 4,295,313, “Building Blocks, Wall Structures Made Therefrom, and Methods of Making the Same”, issued Oct. 20, 1981 to Rassias; U.S. Pat. No. 4,319,440, “Building Blocks, Wall Structures Made Therefrom, and Methods of Making the Same”, issued Mar. 16, 1982 to Rassias; U.S. Pat. No. 2,701,959, “Sectional Block Masonry”, issued Feb. 15, 1955 to Briggs; and Swiss Patent No. 354237, issued Jun. 30, 1961.
One significant drawback of using concrete blocks to form walls in a structure is that surficial covering material often needs to be applied to the surface of the walls. Many common surficial coverings for walls are attached using nails or screws. For example, siding may need to be applied to the outside of the wall, and wallboard, paneling, or other sheet material may need to be applied to the inside of the wall. Known concrete blocks are too hard and brittle to allow commonly-used nails or screws to be used to attach a surficial covering material. As a result, special concrete nails or anchors are typically used to secure wood furring strips or studs to the concrete block wall, and the covering materials are, in turn, fastened to the furring strips or studs. This process of fastening wood furring strips or studs to the block wall and nailing on the covering material to the furring strips is time-consuming, and the concrete blocks do not hold the nails or anchors in place very well. It is not uncommon for one or more of the concrete nails to become loose when a surficial material is nailed in place, compromising the structural integrity of the wall.
Therefore, there existed a need to provide an improved building block with an attachment layer that allows covering materials to be directly attached to the building blocks using conventional nails, screws, or staples. Such a building block is disclosed in U.S. Pat. Nos. 6,085,480 and 6,397,549, which have been assigned to TechBlock International, LLC, the assignee of the instant application. One of the problems in making the building blocks in the two patents referenced above is the use of customized equipment to form the blocks, which is expensive. There are many manufacturing facilities around the world that make many different kinds of known concrete blocks, known in the industry as Concrete Masonry Units (CMUs). It would be desirable to manufacture the block in the two patents cited above using standard machines that manufacture CMUs. However, because the patented block has dimensions that are typically much larger than a CMU, it would be difficult to fabricate a whole block on these known CMU machines without significant modifications.
In addition, fabricating a concrete block that has a substantial amount of compressible material (such as polystyrene) is not suited to existing machines and methods for making CMUs. Existing CMU machines typically use a mold that receives the mix and a head shoe assembly that presses down on the mix, thereby providing substantial compressive force that results in compaction of the block mix. This process is described in the Background of the Invention section of U.S. Pat. No. 7,261,548 issued on Aug. 28, 2007 to John T. Ness. The head shoe assembly compresses the concrete in the mold while simultaneously vibrating the mold, resulting in substantial compression and optimal distribution of the concrete throughout the mold cavity. Because of the compression, the concrete reaches a level of hardness that permits immediate stripping of the finished block from the mold. This is typically done by moving a movable plate that forms the bottom of the mold downward while at the same time moving the head shoe assembly downward, resulting in the head shoe assembly ejecting the block from the mold.
A block mix that includes a substantial amount of compressible material (such as polystyrene) cannot be used in a traditional CMU mold and process, because the compressible material in the mix makes the mix “springy”, meaning the mix can compress as a result of the compression of the compressible material, but when the compressing force is removed, the compressible material tends to uncompress to its original shape. So if such a mix were put into a traditional CMU mold, the compressing step would compress the mix, but when the movable plate moves downward to eject the block from the mold, the force of the compressible material expanding due to removing the compressive force would typically cause the block to blow apart or fall apart and not hold its shape. As a result, new manufacturing methods are needed to mold blocks that include a substantial amount of compressible material on traditional CMU machines.